wasm64: std fails to build with `target-feature=+atomics`

[wooden-worm]

I tried to build an example project for wasm64-unknown-unknown with target-feature=+atomics, but the std failed to build due to

rust/library/std/src/sys/pal/wasm/atomics/futex.rs

Line 1 in 7a08f84

use crate::arch::wasm32;

and

rust/library/std/src/sys/pal/wasm/atomics/thread.rs

Line 22 in 7a08f84

use crate::arch::wasm32;

hardcoding wasm32 arch.

I could get std to build by adding #![feature(simd_wasm64)] to https://github.com/rust-lang/rust/blob/master/library/std/src/lib.rs, and a few cfg checks to import the correct module.

I could work on a PR if that's the right approach.

Meta

rustc --version --verbose:

rustc 1.81.0-nightly (d7f6ebace 2024-06-16)
binary: rustc
commit-hash: d7f6ebacee13b6c03623c4b74197280454ede8de
commit-date: 2024-06-16
host: aarch64-apple-darwin
release: 1.81.0-nightly
LLVM version: 18.1.7

[wooden-worm]

There's another similar problem with building for wasm64 using target-feature=+simd128: portable-simd only supports wasm32

rust/library/portable-simd/crates/core_simd/src/swizzle_dyn.rs

Line 31 in 4e6de37

#[cfg(target_arch = "wasm32")]

[workingjubilee]

that sounds about right as a fix. feel free to PR it!